Static Headspace (HS)

Dynamic Headspace

Spray-and-Trap (ST)

SPME

Membrane Inlet

Purge-and-Trap

Extraction Methods

Advantage : More sensitive than HS

Drawback : 1. Foaming and slowness

of the purging step

2. Large sample volume and

long purging time (10~30 min)

Purge-and-Trap Method

Experimental Aim

To construct an automated ST-

GC system for on-line

determination of dissolved VOCs

in water.

Carboxen 1000 Carboxen 1003

1/16”

Micro-sorbent Trap

Spray-and-Trap Device

Cleaning

Sampling

Mode A

Mode B

Injection

2. Amount of sample

3. Amount of extraction gas that is sampled.

Sensitivity of Mode A

1. Sprying condition

A. Size of droplet

B. Extraction gas flow rate

C. Design of nozzle

D. Introducing a limited amount of sample and extraction gas

Sensitivity of Mode A

Mode A VS. Mode B

A

Purge-and-Trap Device

Analytical conditions for ST and PT

Recoveries of ST methods

Recovery = PTresponse

STresponse

DL, R.S.D, and R2 for BTEX

Species

Chromatograms of ST-GC-ECD

1. CHCl3

2. CCl4

3. CH2Br2

4. CHCl=CCl2

5. CHBrCl2

6. CCl2=CCl2

Conclusion

An automated spray-and-trap device was built in the laboratory.

The studied ST method was validated in comparison with classic PT: recoveries precision, and linearity.

The ST method shows a fast response to abrupt changes in sample quality, which makes it suitable for on-site monitoring of a water body.